Vampire 2019: Editor's Preface

This volume contains a selection of papers presented at the 5th and 6th Vampire Workshops. 

The 5th Vampire Workshop was held on July 13, 2018, as part of FLoC 2018, at the Univesity of Oxford, UK. The program of the 5th Vampire Workshop included an invited talk by Prof. Cesare Tinelli on "Counterexample-Guided Quantifier Instantiation in Logical Theories" and an invited tutorial by Dr. Giles Reger on "Vampire: Where Have We Come From, Where Are We Going". Further, the program also included six contributed talks on recent developments in first-order theorem proving and Vampire. 

The 6th Vampire Workshop was held on July 7, 2019, as an affiliated event of SAT 2019 in Lisbon. Our workshop shared the invited talk of Prof. Roberto Sebastiani on "SMT-Based Weighted Model Integration" with the SMT 2019 workshop. In addition, the program of the 6th Vampire Workshop included an invited talk of Prof. Armin Biere on "SAT, Computer Algebra and Multiplier Verification" and six contributed talks detailing recent development in automated reasoning and verification. 

The current proceedings is a joint proceedings of the 5th and 6th Vampire Workshops. Papers included in the proceedings have been reviewed by the editors of this volume.